It's not always a cut-and-dry decision because balance transfers can be rigged with surprising terms. To start, the cost for switching could be higher than you expected. And as attractive as an offer seems, it might not be the best deal around.

Before jumping on the first mailing you come across, here are answers to some common questions.

Q: Some credit card companies have hiked balance transfer fees from about 3 percent to 5 percent in the past year. How negotiable are those rates?

A: The fees generally aren't negotiable, but you might be able to use the threat of a transferring your balance to get a lower rate on an existing card, said Odysseas Papadimitriou, founder of CardHub.com.

The strategy will likely only work if you have an excellent credit history. So don't expect special favors if you have a record of late payments.

You also want to be realistic and specific in your requests. That means asking to knock more than a few percentage points off your rate probably isn't a smart bet if your credit score is just a so-so 650. Of course, it might not be worth negotiating with your old bank if you have a clearly unbeatable offer for a balance transfer from another bank.

A: It wasn't so long ago that banks limited balance transfer fees at around $100. Such caps are now virtually gone, Papadimitriou said. So if you're transferring a $10,000 balance, the fee could be as high as $300 to $500. You might find the price isn't worth it.

Start by estimating how quickly you plan to pay off the balance. Then figure out the interest charges you'll incur to keep the balance on your existing card for that time.

It may turn out the cost is lower than what you'd pay in transfer fees.

Q: How long do introductory rates on balance transfers typically last?

A: Introductory rates — usually 0 percent for balance transfers — expire much quicker these days. They now generally last six to nine months, about half the time period offered a year ago. The longest offer you'll see is probably about a year, Papadimitriou said.

In some cases, banks might use your credit score to determine how long you get the introductory rate. Either way, be sure you know when the default rate kicks in, and what that rate will be.

You could also trigger the default rate if you're late on a payment. So if you regularly miss due dates, it's something to consider before transferring your balance.

Q: Will my credit score be affected?

A: Applying for a new card dings your credit score in the short term, because it suggests you're in need of money. This category accounts for about 10 percent of your credit score. If you want to avoid taking a hit, check if there are any balance transfer deals offered by your existing cards.